Info
This document is part of an original submission for the RP2350 Hacking Challenge.
For more detailed and up-to-date content, refer to “Laser Fault Injection on a Budget: RP2350 Edition”.
Laser Fault Injection Platform
Overview
A custom fault injection platform has been designed for this project. While this hardware setup may not compete with more professional systems in terms of repeatability, it is likely an order of magnitude cheaper. Fully assembled Laser Fault Injection Platform
The platform can be divided into two subsystems:
- A positioning stage, used to precisely displace the target for observation and laser focusing.
- An optical subsystem, utilized for visualizing the die and focusing high-power laser pulses onto it.
A 3D render of the entire system is available from the Interactive 3D Render Page.
Positioning Stage
The positioning stage is based on the OpenFlexure Delta Stage. OpenFlexure projects are impressive, and I would not have achieved much without them. High-precision mechanical positioning is made possible with simple 3D printer parts and affordable stepper motors.
Minor modifications have been made to the official OpenFlexure Delta Stage:
- The base of the stage was raised to accommodate the custom optical subsystem.
- Heat-set threaded inserts have been added in various locations to support the RP2350 “Backside” Electronic Boards.
Optical Subsystem
The optical subsystem is utilized for visualizing the die and focusing high-power laser pulses onto it.
Note that visible light cannot be utilized, as silicon is not transparent to these wavelengths.
Instead, light with a wavelength of \(1064nm\) is used. This wavelength is traditionally employed for backside fault injection and can also, as demonstrated by Bunnie Wang in Infra-Red, In Situ (IRIS) Inspection of Silicon, be used for visualization.
This subsystem is based on the reflection illumination subsystem from the OpenFlexure project. However, unlike the positioning stage, significant modifications have been implemented.
This fully custom optical system is detailed in the dedicated Laser Fault Optics Page.
Imaging Results
Below are a couple of slightly processed die images obtained from the setup.
While these images may not match the quality of those produced by a professional setup, they are sufficient to align a laser beam on specific features of the die. A first example of the images that can be obtained from the platform Another example
Finally, here is a video of the sample being moved over the optics, revealing various features of the die.
Last update: November 23, 2024